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Flashcards in Electrolytes Deck (30)
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1

Body water distribution

intracellular fluid - 2/3 body water
extracellular fluid - 1/3 body water

2

Osmolality

measures the dissolved particles in a solution
osmoles/kg of water
Na+= 90%
275-295 mOsm/kg

3

ADH effect on Osmolality

osmole receptors in hypothalamus releases ADH if Osmolality is too concentrated

4

Calculated Osmolality

2[Na+] + [glucose/20] + [BUN/3]
gap between calculated osmole & measured osmole >20 is significant
other substances: ethanol, methanol, ethylene glycol, lactate etc etc

5

Blood Volume regulation

Renin-angiotensin-aldosterone
atrial natuiretic peptide- BNP tries to regulate blood pressure
volume receptors independent of osmolality- will stimulate ADH release
GFR- increase or decrease w/ volume
sodium concentration - its reabsorption brings kidney filtrate back into blood

6

Renin-angiotensin-aldosterone (RAA)

renin- hormone from kidney once released it acts on angiotensinogen to make angiotensinogen 1 (from liver) to go to angiotensinogen 2 which acts on blood pressure: acts on adrenal gland for aldosterone, constrict blood vessels, ADH secretion, H2O retention
aldosterone is a major hormone in the conservation of Na+ by the kidney, increase blood pressure
ADH- conserves water, decreases blood pressure

7

Major electrolytes

Na+, K+, Cl-, tCO2

8

function of major electrolytes

maintain osmotic pressure & hydration
maintain pH
regulate heart rate & muscle action
involved in ox-reduc reactions
essential co-factors for some enzymes

9

Na+ general characteristics

major cation in ECF
renal threshold 110-130 mmoles/L
aldosterone, angio II, ADH regulate Na+ levels
renal mechanims fosters Na+ retention (!) & excretion of H+, Cl- ion
Na+K+ ATPase

10

Na+ K+ ATPase

3 Na+ out of cell & 2 K+ into cell

11

Na+ regulation depends on :

intake of water, due to thirst & plasma osmoles
excretion of water affected by ADH response to blood volume or osmolality
blood volume status, affects Na+ excretion via ADH, aldosterone & Angio II

12

Hyponatremia

decreased Na+ <135 mmol/L
dilutional due to water retention (acute/chronic renal failure)
vomiting/ diarrhea
Nephrotic syndrome
SIADH (syndrome of inappropriate ADH) - increased ADH = increased water retention & decreased Na+

13

Hypernatremia

increased Na+
intake is high
dehydration

14

Na+ methods of analysis

ion selective electrodes that use Na+ sensitive glass
Slide ISE - uses potential difference
serum range - 136-145 mmol/L

15

Potassium K+

major intracellular cation ( 20x K+ inside vs in plasma)
increase serum K+ w/ exercise (cell break down)
excreted by kidney

16

K+ functions

regulate neuromuscular excitability
contraction of heart, ICF volume, H+ concentration

17

Hypokalemia

decreased K+
GI loss - vomiting, diarrhea, malabsorption
renal loss- nephritis, cushings, ^ aldosterone
decreased intake
cellular shift - alkalosis (!)

18

Hyperkalemia

^^ K+
decreased renal excretion - renal insufficiency , DM
cellular shift - acidosis (!)
increased intake
platelet ruptures/ transfusions

19

Potassium methodology & range

ion selective electrode using valinomycin impregnanted membrane
3.5-5.1 mmol/L serum

20

Chloride Cl- characteristics & function

major extracellular anion
important in osmotic pressure, blood volume & electrical neutrality (chloride shift)

21

Chloride shift

Cl- ions exchange w/ HCO- ions as CO2 is transported in/ouit of RBC
maintains electrical neutrality within the RBC

22

Hypochloridemia

salt losing renal disease
adlosterone deficiency: not absorbing Na+
prolonged vomiting
diabetic Ketoacidosis (!): too much H+ being formed & Cl- is being used to neutralize pH

23

Hyperchloridemia

excess HCO3- loss
GI losses
renal tubular acidosis: kidney damage that prevents exchange
metabolic acidosis (!)

24

Chloride analyzer methods

titration methods
ion selective electrodes - chloride will bind w/ silver ions Ag1_

25

tCO2 general

90% HCO3-
important as part of CO2 buffer system in the body
buffers acids formed during normal metabolism
regulated by kidneys - almost all reabsorbed bc its such an efficient buffer

26

CO2 buffer reaction

CO2 + H2O H2CO3 H+ + HCO3-
tissues: give up CO2
lungs: breath out CO2
enzyme: carbonic anhydrase

27

Hypocapnia

low tCO2 (<23)
metabolic ACIDOSIS - loss of CO2 from blood buffer system

28

Hypercapnia

high tCO2 (>30)
metabolic ALKALOSIS - increased CO2 in the blood

29

total CO2 enzymatic method

substrate: patient HCO3-
enzymes: PEP carboxylase, malate dehydrogenase
read: NAD
specimens must be handled correctly to avoid losing CO2 (aka loose cap)

30

Anion gap

Na+ - (Cl+tCO2) = 7-16 range
>16 : uremia, renal failure, ketoacidosis (+>-)
<7: hypoalbuminemia, hypercalcemia